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(12) United States Patent Campbell et al.

(54) AEROSPACE LASER IGNITION/ABLATION VARIABLE HIGH PRECISION THRUSTER

(75) Inventors: Jonathan W. Campbell, Madison, AL (US); David L. Edwards, Huntsville, AL (US); Jason J. Campbell, Harvest, AL (US)

(73) Assignee: The United States of America as Represented by the Administrator of the National Aeronautics and Space Administration, Washington, DC (US)

(*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 1166 days.

(21) Appl. No.: 12/862,510

(22) Filed: Aug. 24, 2010

(51) Int. Cl. F03H 1/00 (2006.01) B64G 1140 (2006.01) G21D 5102 (2006.01)

(52) U.S. Cl. CPC B64G1/406 (2013.01); F03H1/00 (2013.01);

G21D 5102 (2013.01)

(58) Field of Classification Search CPC ........... B64G 1/406; F03H 1/00; F03H 99/00;

G21D 5/02; F02K 9/68 USPC ......... 60/202, 203.1, 253, 255, 204; 244/164,

244/169; 315/111.01, 111.11, 111.21, 315/111.31, 111.41, 111.51, 111.61,

315/111.71, 111.81, 111.91; 102/202, 200, 102/201, 202.5, 328, 329, 330, 440; 89/7;

86/20.12 See application file for complete search history.

100

(lo) Patent No.: US 9,021,782 B1 (45) Date of Patent: May 5, 2015

(56) References Cited

U.S. PATENT DOCUMENTS

2,114,574 A 4/1938 Rickenbacher 2,836,919 A 6/1958 du Bois 3,625,154 A * 12/1971 Gawlicketal ................ 102/531 4,045,269 A * 8/1977 Voss et al ...................... 156/221 4,745,859 A 5/1988 Kyoung et al. 4,870,903 A 10/1989 Caret et al. 4,917,014 A 4/1990 Loughry et al. 5,036,767 A 8/1991 Folsom et al. 5,459,548 A 10/1995 Matsuda et al. 6,047,643 A 4/2000 Benner et al. 6,530,212 B1 * 3/2003 Phipps et al . ................ 60/203.1

2007/0012665 Al* 1/2007 Nelson et al . ............ 219/121.69

* cited by examiner

Primary Examiner Thomas Denion Assistant Examiner Vikansha Dwivedi (74) Attorney, Agent, or Firm Absolute Technology Law Group, LLC; James J. McGroary

(57) ABSTRACT

A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation pro-pulsion system may be scaled for use in small and large applications.

27 Claims, 12 Drawing Sheets

20 22

https://ntrs.nasa.gov/search.jsp?R=20150009340 2018-07-29T04:13:11+00:00Z

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US 9,021,782 B1

AEROSPACE LASER IGNITION/ABLATION VARIABLE HIGH PRECISION THRUSTER

FEDERAL RESEARCH STATEMENT

The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.

TECHNICAL DESCRIPTION OF THE INVENTION

The present invention relates generally to the field of rocket propulsion, and more specifically to a device utilizing a pulsed, variable, high precision laser ignition/ablation thruster for propulsion.

BACKGROUND OF THE INVENTION

Aerospace propulsion systems are known in the art. Rock-ets are propelled using either liquid or solid fuel chemical propulsion or some combination of both. Each system has unique advantages and disadvantages. Liquid fuel chemical propulsion systems can be throttled and are capable of being turned on and off. In addition, the thrust levels can be varied resulting in greater efficiency and flexibility during operation. Liquid propulsion systems, however, generally have a higher mass and require more complex and costly components than do solid rocket systems.

Solid rocket propulsion systems have a lower level of con-trollability than liquid rocket propulsion systems. Unlike liq-uid rocket propulsion systems, solid rocket propulsion sys-tems cannot be turned off once lit. Once the propulsion system is turned on, it will continue to burn until all fuel is used up. The inability to be turned off limits the operational envelope and presents a potential safety hazard.

Solid rocket propulsion systems respond more quickly than liquid fuel propulsion systems once turned on. In addi-tion, solid rocket propulsion systems generally have higher performance than liquid fuel propulsion systems, providing a greater thrust/specific impulse per fuel weight. The weight and performance of the fuel is a significant factor for aero-space craft as it is estimated that each additional pound adds $10,000 to the cost of putting a payload into space.

Propulsion systems are usually tailored to meet certain mission requirements and specifications and may have to start and stop a limited number of times. As space applications continue to diversify, scalability in propulsion systems is important and allows rocket builders to more effectively tailor their designs to a given application.

Depending on the mission, liquid propulsion systems also may have inconvenient storage requirements or limited shelf life and may be inconvenient for modular packaging. For example, liquid systems may require the continued cooling for cryogenic fuels with associated insulation and storage tanks while solids would only need a "room temperature" environment.

It is very desirable to have a propulsion system that cap-tures the controllability of liquid propulsion and the high performance of solid propulsion.

It is very desirable to have a propulsion system that is scalable and able to be tailored to a variety of applications, which allows for variable thrust or specific impulse levels.

2 It is very desirable to have a propulsion system that can be

started, stopped and restarted as needed, and which aids in providing high precision performance.

It is very desirable to have a propulsion system with modu-s lar design for convenient resupplying, refueling and modify-

ing of ignition/ablation material. It is further desirable to have a propulsion system that

allows multiple systems to be integrated into a single craft.

io SUMMARY OF THE INVENTION

The present invention is a pulsed, variable, high precision laser ignition/ablation thruster, which captures the advan-tages from both liquid and solid propulsion. A reinforced,

15 transparent tape in back carries a volume of propellant or ablation material into the ignition/ablation chamber. A suffi-ciently intense laser pulse passes through a transparent, high temperature, high pressure laser window and through the transparent carrier tape, striking the back surface of the target

20 propellant/ablation material. If a propellant is used, it is ignited and the expanding gas passing through a rocket nozzle generates thrust. If an ablative material such as paraffin is used, the substance is converted to an expanding gas that passes through a rocket nozzle producing thrust.

25 Once this event is complete, the tape then moves a new target element into the ignition/ablation chamber and the event is repeated. Many events may take place per second creating high average thrust and specific impulse. Tape speed for a given propellant or ablative substance determines thrust

30 level. This process can be employed on size scales ranging from very small to very large, and may be synchronized with a computer control.

GLOSSARY 35

As used herein, the term "containment border structure" refers to a component of a transport structure that encloses ignition or ablation material.

As used herein, the term "flammable" means subject to 4o burning when exposed to heat.

As used herein, the term "highly resilient material' refers to a material that is tolerant of high temperatures, pressure, and tension, is able to withstand vacuum environments and environments with an extreme range of temperatures, and

45 which is resistant to tangling. Examples of highly resilient material include, but are not limited to para-aramid synthetic fiber (e.g., Kevlar®) and polyimide (e.g., Kapton(k).

As used herein, the term "nonconductive" means not capable of conducting an electrical current.

50 As used herein, the term "opaque" means a material that absorbs a laser beam rather than allowing it to pass through.

As used herein, the term "propellant material' refers to a substance capable of being ignited or ablated.

As used herein, the term "reel' refers to a rotating compo-55 nent used for storing, dispensing, and/or protecting a trans-

port structure. As used herein, the term "reinforcing members" refers to

material added to a layer of propellant tape to add strength. Reinforcing members may include, but are not limited to wire

60 mesh, metallic wires, wire ribbon, wire threads, Kevlar® threads, and nylon threads.

As used herein, the term "synthetic fiber" refers to a mate-rial that is stronger than steel and which is tolerant to high pressure and temperature. Examples of synthetic fibers

65 include, but are not limited to para-aramid fibers (e.g., Kev-lar® and Twaron(k), polymer fibers, polyethylene fibers, nylon fibers, carbon fibers, and glass fibers.

US 9,021,782 B1 3

4

As used herein, the term "transport structure" or "propel- claims and as a representative basis for teaching one of ordi-

lant tape" refers to a component that moves propellant mate- nary skill in the art to employ the present invention. rial through an ignition/ablation chamber. It should be understood that the drawings are not necessar-

ily to scale; instead, emphasis has been placed upon illustrat- BRIEF DESCRIPTION OF THE DRAWINGS 5 ing the principles of the invention. In addition, in the embodi-

ments depicted herein, like reference numerals in the various

FIG. 1 illustrates an exemplary embodiment of a laser drawings refer to identical or near identical structural ele- ignition/ablation propulsion system.

FIG. 2a illustrates a top view of a first exemplary embodi-ment of propellant tape for a laser ignition/ablation propul-sion system.

FIG. 2b illustrates a side view of a first exemplary embodi-ment of propellant tape for a laser ignition/ablation propul-sion system.

FIG. 2c illustrates a top view of a second exemplary embodiment of propellant tape for a laser ignition/ablation propulsion system.

FIG. 2d illustrates a top view of a third exemplary embodi-ment of propellant tape for a laser ignition/ablation propul-sion system.

FIGS. 3a through 3d illustrate perspective views of exem-plary shapes of propellant targets.

FIG. 4a illustrates a back view of an exemplary embodi-ment of a propellant tape storage feed reel for a laser ignition/ ablation propulsion system.

FIG. 4b illustrates a front view of an exemplary embodi-ment of a propellant tape storage feed reel for a laser ignition/ ablation propulsion system.

FIG. 5a illustrates a back view of an exemplary embodi-ment of a propellant tape storage takeup reel for a laser ignition/ablation propulsion system.

FIG. 5b illustrates a front view of an exemplary embodi-ment of a propellant tape storage takeup reel for a laser ignition/ablation propulsion system.

FIG. 6 illustrates a cross sectional view of an exemplary embodiment of an ignition/ablation chamber for a laser igni-tion/ablation propulsion system.

FIG. 7 illustrates an exemplary embodiment of a fiber optic transmission of a laser pulse of a laser ignition/ablation pro-pulsion system.

FIG. 8 illustrates an exemplary embodiment of a packaging option for an ignition/ablation propulsion system.

FIG. 9a illustrates an exemplary embodiment of a configu-ration of a plurality of packaged ignition/ablation propulsion systems.

FIG. 9b illustrates a second exemplary embodiment of a configuration of a plurality of packaged ignition/ablation pro-pulsion systems.

FIG. 10 illustrates an exemplary embodiment of an igni-tion/ablation propulsion system having multiple ignition chambers.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the present invention, references are made in the text to exem-plary embodiments of a laser ignition/ablation propulsion system, only some of which are described herein. It should be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent materials, components, and placement may be used. The inclusion of additional ele-ments may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the

ments. Moreover, the terms "substantially" or "approximately" as

to used herein may be applied to modify any quantitative repre-sentation that could permissibly vary without resulting in a change to the basic function to which it is related.

FIG. 1 illustrates an exemplary embodiment of laser igni- 15 tion/ablation propulsion system 100 comprised of laser 10,

laser window 35, target containment walls 42a, 42b, ignition chamber 40, storage feed reel 20, storage takeup reel 22, and propellant tape 25. Laser 10 is positioned so that laser pulse 12 passes through laser window 35 between target contain-

20 ment walls 42a, 42b. Propellant tape 25 contains propellant targets 30 (See FIG.

2a), comprised of ignition/ablation material, at regular inter-vals. Propellant tape 25 is wound on storage feed reel 20, which unwinds, feeding propellant tape 25 under laser 10.

25 Propellant tape 25 is rewound on storage takeup reel 22 after propellant targets 30 have been ignited/ablated.

When a propellant target 30 is positioned between target containment walls 42a, 42b, propellant tape 25 pauses and laser 10 fires sending laser pulse 12 through laser window 35.

so Laser pulse 12 strikes the surface of propellant target 30 igniting or ablating it, resulting in a thrust impulse. Propellant tape 25 then carries another propellant target 30 over ignition chamber 40.

The movement of propellant tape 25 is synchronized to the 35 firing of laser 10 so that a new propellant target is in position

each time laser 10 fires. The resulting thrust/specific impulse may be precisely controlled by varying the speed of propel-lant tape 25 and the firing of laser 10.

In addition, the frequency of laser pulse 12 will be a direct 40 function of the burn rate of propellant target 30. The burn of

propellant target 30 must be complete prior to moving a new propellant target into ignition chamber 40. The ignition tran-sient time, steady-state burn-time, and tail-off transient for each propellant target 30 needs to be considered. Heat trans-

45 fer must also be considered. In the embodiment shown, laser window 35 is integrated

with ignition chamber 40, which is comprised of a material that is tolerant of high temperatures and high pressure, and is transparent to the wavelength of laser pulse 12. Laser window

5o 35 prevents the hot gas which results from ignition/ablation from escaping through the top of ignition chamber 40 helping to control the outflow of gas by forcing it to pass through nozzle 85. Laser window 35 may be comprised of a material including, but not limited to polycarbonate resin thermoplas-

55 tic (e.g., Lexan(k), glass, plastic, resin, quartz, silicon, or any other material(s) that is transparent to a laser beam and is tolerant to high temperatures and pressure.

FIG. 2a illustrates a top view of a first exemplary embodi-ment of propellant tape 25 for laser ignition/ablation propul-

60 sion system 100. Propellant tape 25 is comprised of a plurality of discrete propellant targets 30 positioned at regular intervals between transparent back cover 26 and transport layer 27. Propellant tape 25 is positioned so that transparent back cover 26 faces upward toward laser pulse 12 (see FIG. 2b).

65 The design of propellant tape 25 is crucial. Propellant tape 25 must protect propellant targets 30 during storage and when a propellant target is ignited/ablated. Propellant tape 25 must

US 9,021,782 B1 5

6 prevent the contingency of other propellant targets igniting/

Transport layer 27 is the primary drive tape and must be

ablating in an uncontrolled chain reaction. thick enough to allow propellant tape 25 to be driven at a high In the embodiment shown, transparent back cover 26 is a rate of speed. In addition, transport layer 27 must be imper-

transparent, heavy duty, relatively thick foundation tape layer vious to being burned cutting propellant tape 25 in multiple that is transparent to the wavelength of laser pulse 12 (not 5 pieces, which would affect the movement of propellant tape shown). Transparent back cover 26 must be comprised of a

25.

material that is robust and thick enough to tolerate the tran- Transparent back cover 26 and transport layer 27 hold sient temperature and pressure that occurs during ignition/

propellant targets 30 firmly in position during movement of

ablation. propellant tape 25 and further enables propellant targets 30 to Openings are cut in transport layer 27 to the desired size of io be accurately aligned between laser widow 35 (not shown)

ignition/ablation material. The openings are then covered

and ignition chamber 40. with a nonflammable membrane 31, which is secured to trans- In the embodiment shown, propellant tape further includes port layer 27. The membrane 31 may be bonded, glued, or sprocket holes 28, which correspond to inner gear sprockets sewn to the front of transport layer 27. Containment border

66 of takeup reel 20 (not shown) and aid in the unraveling of

structures 29 are mounted to transport layer 27 so that they 15 propellant tape 25. surround the openings. Ignition/ablation material is then

In the embodiment shown, propellant targets 30 are circu-

attached to transport layer 27 forming propellant targets 30. lar, but in other embodiments may be of another shape includ- In various embodiments, propellant targets 30 may be

ing, but not limited to doughnut-shaped, oval, square, rectan-

comprised of ignition or ablation material. Examples of igni- gular, star-shaped, or may have an undefined shape or be tion material include, but are limited to shuttle solid rocket 20 randomly shaped. In other embodiments, propellant targets booster propellant, Ammonium Perchlorate Composite Pro- 30 have an array pattern so that one element of the array pellant, or another solid rocket propellant known in the art. pattern is ignited and subsequently ignites other elements of For lower thrust levels, ablation material, such as paraffin the array. The cross section of propellant target 30 may also may be used. Propellant targets 30 may be attached to trans- vary. For example, propellant target 30 may be concave or parent back cover 26 via adhesive properties of the ignition/ 25 convex in order to optimize performance and cost. In various ablation material or may be glued to transparent back cover embodiments, propellant tape 25 may further include 26 using adhesive. optional filler material 33 to smoothen propellant tape 25 so it

Transport layer 27 is secured to transparent back cover 26

is better adapted for winding/unwinding on storage feed reel so that propellant targets 30 are secured between transparent

20 and storage takeup reel 22.

back cover 26 and transport layer 27. Transport layer 27 and so In embodiments where ablation material, rather than igni- transparent back cover 26 may be secured together by bond- tion material, is used, the ablation material may be located ing, gluing, sewing, or another attachment means known in continuously along the propellant tape. the art to form propellant tape 25. In various embodiments, one or more additional layers of

Transport layer 27 faces toward ignition chamber 40 (not

transparent layers with square or circular openings may be shown). When propellant target 30 is ignited/ablated, propel- 35 joined continuously to the transparent back cover 26 for addi- lant target 30 bursts through the membrane 31 into ignition tional positioning and support of propellant tape 25. In still chamber 40. other embodiments, inserts are attached to transparent back

In the embodiment shown, transparent back cover 26, cover 26 and are used to surround propellant targets 30. These transport layer 27, and the membrane 31 may be comprised of

inserts may be opaque to the wavelength of laser pulse 12.

conductive materials, nonconductive materials, or a combi- 40 In various embodiments, transparent back cover 25 and nation thereof. For example, transparent back cover 26 and

transport layer 27 materials may vary depending on the igni-

transport layer 27 may be comprised entirely of nonconduc- tion/ablation material used for propellant targets 30 and the tive materials including, but not limited to para-aramid syn- associated ignition/ablation temperatures and pressures. thetic fiber (e.g., Kevlar®) and polyimide (e.g., Kapton(k). The spacing and size of propellant targets 30 on propellant The use of nonconductive materials prevents an electrical 45 tape 25 is dependent upon a number of factors including, but current from traveling through propellant tape 25 causing not limited to the ignition/ablation material being used, the propellant targets other than the one in the ignition chamber to amount of ignition/ablation material in each propellant target, ignite. In various other embodiments, transparent back cover the length of propellant tape 25, the speed that propellant tape 26 and/or transport layer 27 may further contain reinforcing

25 moves through the ignition chamber, operation time, and

members which are nonconductive (e.g., para-aramid syn- 50 the application for which laser ignition/ablation propulsion thetic fibers, nylon threads) or nonconductive (e.g., metallic system 100 is being used. Propellant targets 30 should be threads). The use of only nonconductive materials may be

located far enough apart so that one propellant target can be

desirable to maximize safety and reliability; however, metal- ignited without the risk of igniting adjacent propellant targets. lic reinforcement may be required for maximum perfor- If the propellant targets are located too close together, ignit- mance. 55 ing/ablating one propellant target may cause a second propel-

Similarly, the membrane 31 may be comprised of a rela- lant target to ignite/ablate outside of the ignition chamber. tively thin nonconductive material including, but not limited

In an exemplary embodiment, propellant targets are uni-

to plastic film, polyimide film, or other plastic film, and/or a

formly spaced. In embodiments where the desired thrust conductive material including, but not limited to aluminum variations for a mission application are known in advance, foil or another type of metallic foil. 6o non-uniformed spacing of propellant targets may be desired.

The membrane 31 enhances the storage life of propellant

FIG. 2b illustrates a side view of a first exemplary embodi- targets 30. In various embodiments, the membrane 31 is com- ment of propellant tape 25 showing the direction that laser prised of aluminum foil or another type of foil, and/or may be pulse 12 passes through propellant tape 25. comprised of multiple layers (e.g., a conductive layer and a

FIG. 2c illustrates a top view of a second exemplary

nonconductive layer). In various embodiments, an additive 65 embodiment ofpropellant tape 25. In the embodiment shown, may be added inside the membrane 31 to further increase the propellant tape 25 further includes wires 50 between propel- storage capability of propellant targets 30. lant targets 30 and sprocket holes 28. Wires 50 provide addi-

US 9,021,782 B1 7

8 tional reinforcement for extremely energetic events and only

driven by a single electric motor. Driving both reels allows for

minimally affect the flexibility of propellant tape 25. precise control of the tension of propellant tape 25. The con- FIG. 2d illustrates a top view of a third exemplary embodi- troller would sense this level of tension and manage it accord-

ment of propellant tape 25. In the embodiment shown, pro- ingly to minimize the chance of pulling apart the tape. pellant tape 25 further includes wire ribbon 52 for additional 5 FIG. 5b illustrates a front view of an exemplary embodi- reinforcement. In various embodiments, propellant tape 25

ment of propellant tape storage takeup reel 22 showing pro-

may be reinforced by embedding steel, para-aramid synthetic pellant tape 25 and inner gear sprockets 66 which correspond fiber, or other high tensile strength wires or threads which run to sprocket holes 28 (not shown) on propellant tape 25. the length of propellant tape 25. A mesh matrix may also be

FIG. 6 illustrates a cross sectional of an exemplary embodi-

used to reinforce propellant tape 25. io ment of ignition chamber 40 showing laser window 35, target The addition of metallic elements (e.g., threads, wires, wire containment walls 42a, 42b, tape containment walls 74a, 74b,

ribbon) provides a strong border for propellant tape 25

synchronizing mechanism 78a, 78b, propellant tape 25, pro- decreasing the likelihood that propellant tape 25 will be cut by pellant target 30, expended propellant target 32, and laser ignition/ablation. The width and thickness of propellant tape pulse 12. 25 may also be adjusted to decrease the likelihood of propel- 15 Target containment walls 42a, 42b and tape containment lant tape 25 being cut. walls 74a, 74b isolate the ignition/ablation event from the rest

FIGS. 3a through 3d illustrate perspective views of exem- of propellant tape 25, from other propellant targets 30, and plary shapes of propellant targets. FIG. 3a illustrates propel- from storage feed reel 20 and storage takeup reel 22. Target lants that are convex, FIG. 3b illustrates propellant targets that containment walls 42a, 42b seal off the ignition chamber 40 are concave, FIG. 3c illustrates donut-shaped propellant tar- 20 during an ignition/ablation event. During the ignition/abla- gets and FIG. 3d illustrates propellant targets that are tion event, the only escape path for expanding gases is arranged in an array. Propellant targets may be shaped and

through nozzle 85 (not shown).

arranged in order to optimize performance and cost for each

Synchronizing mechanisms 78a, 78b are movable and are application. used to place additional pressure on propellant tape 25. Syn-

FIG. 4a illustrates a back view of an exemplary embodi- 25 chronizing mechanisms 78a, 78b are lowered creating an ment of propellant tape storage feed reel 20. Propellant tape additional barrier between the ignited/ablated propellant tar- 25 is wound on storage feed reel 20 and fed into ignition get 30 and the adjacent propellant targets and reels 20, 22 (not chamber 40 (not shown) and then rewound on storage takeup shown) helping to maintain the structure of propellant tape 25 reel 22 (FIGS. 3a and 3b). and to force the resulting hot gas into through nozzle 85 (not

In the embodiment shown, storage feed reel 20 is driven by 30 shown). Synchronizing mechanisms 78a, 78b are then gearbox 60 and motor 62, which is controlled by controller 64

retracted to allow propellant tape 25 to carry another propel-

(e.g., a computer). Controller 64 is isolated outside of the

lant target 30 into ignition chamber 40. In the embodiment contained area where ignition/ablation occurs. Controller 64

shown, synchronizing mechanisms 78a, 78b are lowered and

may be hard-wired or wireless and a single controller may be retracted using a spring; however, in other embodiment capable of controlling multiple laser ignition/ablation propul- 35 another mechanism, such as movable pistons, may be used. sion systems. In an exemplary embodiment, controller 64

In the embodiment shown, tape containment walls 74a,

controls all aspects of thruster operation and communicates

74b are fixed and target containment walls 42a, 42b are mov- with reel motors and laser 10 (not shown), as well as the able and are synchronized to lift away from propellant tape 25 spacecraft controller. One controller may operate several

prior to propellant tape 25 moving, allowing a new propellant

reels depending on the mission application. 40 target 30 to be brought into ignition chamber 40. Propellant FIG. 4b illustrates a front view of an exemplary embodi- tape 25 also carries away all post-ignition/ablation contami-

ment of propellant tape storage feed reel 20 showing propel- nants preventing them from clouding laser window 35. lant tape 25, the direction of unraveling, and inner gear

FIG. 7 illustrates an exemplary embodiment of fiber optic

sprockets 66. Inner gear sprockets 66 correspond to sprocket

transmission of laser pulse 12. In the embodiment shown, holes 28 (not shown) in propellant tape 25 aiding in the 45 laser 10 is not located in the proximity of propellant target 30 placement and unraveling of propellant tape 25. and fiber optic cable 90 is used to transmit laser pulse 12 from

FIG. 5a illustrates a back view of an exemplary embodi- laser 10 to propellant target 30. ment of propellant tape storage takeup reel 22. In the embodi- Fiber optic cable 90 is capable of carrying a sufficiently ment shown, storage takeup reel 22 is driven by gearbox 60

intense laser pulse to achieve ignition/ablation, enabling

and motor 62, which is controlled by controller 64. In the 50 many packaging options for laser 10. Utilizing fiber optics embodiment shown, controller 64 controls all aspects of

enables the use of remote lasers from either the ground, space,

thruster operation. internal to the ignition/ablation propulsion system 100, or In the embodiment shown, both storage feed reel 20 and

from anywhere with a suitable environment to power the

storage takeup reel 22 are comprised of light, tough, heat- thruster. resistant materials. Storage feed reel 20 and storage takeup 55 FIG. 8 illustrates a second exemplary embodiment of a reel 22 may be comprised of nonconductive material includ- packaging option for ignition/ablation propulsion system 100 ing, but not limited to high strength plastic such as Kapton®, showing controller 64, laser 10, ignition chamber 40, storage or carbon composite, and/or a conductive material including, feed reel 20, storage takeup reel 22, and nozzle 85. The but not limited to aluminum, beryllium, and combinations

direction in which nozzle 85 points determines the direction

thereof. In addition, storage feed reel 20 protects propellant 60 of thrust. Nozzle 85 is controlled by controller 64. tape 25 from outside contamination and humidity. In the embodiment shown, ignition/ablation propulsion

In various embodiments, one or both reels may be pow- system 100 has one nozzle; however, in other embodiments, ered. For example, only storage takeup reel 22 is driven by an

ignition/ablation propulsion system 100 may include more

electric motor and the tension from storage takeup reel 22 is than one nozzle pointed in the same or in varying directions. used to unwind propellant tape 25 from storage feed reel 20. 65 The packaging option for ignition/ablation propulsion sys- In an exemplary embodiment, both storage feed reel 20 and

tem 100 shown in FIG. 8 enables convenient packing into

storage takeup reel 22 have gearing which allows them to be thruster modules with relatively long storage life. In addition,

US 9,021,782 B1 9

10

modular packaging allows for replenishment of attitude con- 8. The apparatus of claim 5 wherein said reinforcing mem-

trol propulsion subsystems (e.g., for a return mission). If

bers are comprised of a material selected from a group con-

scaled up, these modules could be used to push a potentially sisting of aluminum, titanium, steel, stainless steel, Kevlar®,

hazardous asteroid, meteoroid, or comet away avoiding a nylon, and synthetic fibers. potential impact with Earth. 5 9. The apparatus of claim 1 wherein said membrane is a

FIG. 9a illustrates an exemplary embodiment of a configu- material selected from a group consisting of plastic film,

ration of a plurality of packaged ignition/ablation propulsion polyimide film, plastic foil, aluminum foil, and tin foil.

systems 100. In the embodiment shown, ignition/ablation

10. The apparatus of claim 1 wherein said containment

propulsion systems 100 are stacked to achieve greaterperfor- border structures are uniformly spaced. mance. io 11. The apparatus of claim 1 wherein said containment

FIG. 9b illustrates a second exemplary embodiment of a

border structures are non-uniformly spaced.

configuration of a plurality of packaged ignition/ablation pro- 12. The apparatus of claim 1 wherein spacing of said con-

pulsion systems 100 combined to thrust in several directions. tainment border structures is dependent on said propellant

In another embodiment, a movable mirror may be used to material, amount of said propellant material, amount of thrust ignite/ablate all modules using a single laser pulse. 15 required, and scale of system in which said apparatus is used.

FIG. 10 illustrates an exemplary embodiment of an igni- 13. The apparatus of claim 1 wherein said containment

tion/ablation propulsion system having multiple ignition

border structures are spaced so that said propellant material

chambers 40 positioned along a single propellant tape 25. In contained in said containment border structure is isolated

various embodiments, multiple ignition chambers 40 may

from propellant material contained in adjacent containment share one or more pairs of storage feed and storage takeup 20 border structures. reels, one laser, and one controller. 14. The apparatus of claim 1 wherein said propellant mate-

What is claimed is: rial is ablation material and is placed continuously along said 1. A propellant transport structure apparatus for a space- transport layer.

craft comprised of:

15. A laser ignition/ablation propulsion system comprised • transport layer having an elongated shape and a plurality 25 of:

of openings; • laser;

• substantially transparent back cover, corresponding in • laser ignition/ablation chamber having a window, said size to said transport layer; window being transparent to a laser beam, and at least

• plurality of containment border structures sandwiched

one containment wall seal; between said transport layer and said substantially trans- so propellant material; and parent back cover; and

a transport structure for transporting said propellant mate-

• membrane affixed to a front side of said transport layer rial into said laser ignition/ablation chamber, said trans-

such that said membrane overlays said plurality of open- port structure comprised of: ings of said transport layer, • transport layer having an elongated shape and a plu-

wherein each of said plurality of openings is surrounded by 35 rality of openings;

one of said plurality of containment border structures, • substantially transparent back cover, corresponding in

wherein each of said plurality of openings further includes size to said transport layer;

a propellant material, said propellant material being • plurality of containment border structures sandwiched

affixed to said substantially transparent back cover and

between said transport layer and said substantially contained by one of said plurality of containment border 40 transparent back cover; and structures, • membrane affixed to a front side of said transport layer

wherein one of said plurality of containment border struc- such that said membrane overlays said plurality of

tures encloses said propellant material along a length

openings of said transport layer, and a width of said transport layer, wherein each of said plurality of openings is surrounded

wherein each containment border structure is separated by 45 by one of said plurality of containment border struc-

a discrete distance from any other containment border tures, structure, wherein each of said plurality of openings further

wherein said containment border structure is affixed to a

includes a propellant material, said propellant mate-

back side of said transport layer and to a front side of said

rial being affixed to said substantially transparent substantially transparent back cover, 50 back cover and contained by one of said plurality of

wherein said membrane is sufficiently thin that an ignited

containment border structures,

propellant material bursts through said membrane to wherein one of said plurality of containment border propel a spacecraft, structures encloses said propellant material along a

wherein said membrane comprises a material which is not

length and a width of said transport layer, flammable. 55 wherein each containment border structure is separated

2. The apparatus of claim 1 wherein said substantially

by a discrete distance from any other containment transparent back cover is transparent to a laser beam. border structure,

3. The apparatus of claim 1 wherein said transport layer is wherein said containment border structure is affixed to a comprised of a highly resilient material. back side of said transport layer and to a front side of

4. The apparatus of claim 1 wherein said transport layer is 60 said substantially transparent back cover, nonconductive. wherein said membrane is sufficiently thin that an

5. The apparatus of claim 1 wherein said transport layer is

ignited propellant material bursts through said mem- reinforced with reinforcing members. brane to propel a spacecraft,

6. The apparatus of claim 5 wherein said reinforcing mem- wherein said membrane comprises a material which is bers are metallic. 65 not flammable.

7. The apparatus of claim 5 wherein said reinforcing mem- 16. The system of claim 15 wherein said transport structure bers are non-metallic. is rigid.

US 9,021,782 B1 11

17. The system of claim 15 wherein said transport structure is flexible.

18. The system of claim 15 wherein said transport structure is adapted for mounting on a reel.

19. The system of claim 15 wherein said window is com-prised of a material selected from a group consisting of glass, thick glass, plastic, resin, quartz, silicon, and polycarbonate resin thermoplastic.

20. The system of claim 15 wherein said transport structure further includes optional filler material.

21. A laser ignition/ablation propulsion system comprised of:

• laser; • laser ignition/ablation chamber having a window, said

window being transparent to a laser beam, and at least one containment wall seal;

• transport structure for transporting said propellant mate-rial into said laser ignition/ablation chamber comprised of: • transport layer having an elongated shape and a plu-

rality of openings; • substantially transparent back cover, corresponding in

size to said transport layer; • plurality of containment border structures sandwiched

between said transport layer and said substantially transparent back cover; and

• membrane affixed to a front side of said transport layer such that said membrane overlays said plurality of openings of said transport layer,

wherein each of said plurality of openings is surrounded by one of said plurality of containment border struc-tures,

wherein each of said plurality of openings further includes a propellant material, said propellant mate-rial being affixed to said substantially transparent

12 back cover and contained by one of said plurality of containment border structures,

wherein one of said plurality of containment border structures encloses said propellant material along a

5 length and a width of said transport layer, wherein each containment border structure is separated

by a discrete distance from any other containment border structure,

wherein said containment border structure is affixed to a

10 back side of said transport layer and to a front side of said substantially transparent back cover,

wherein said membrane is sufficiently thin that an ignited propellant material bursts through said mem-brane to propel a spacecraft,

15 wherein said membrane comprises a material which is not flammable;

• feed reel; and • takeup reel. 22. The system of claim 21 wherein said feed reel and said

20 takeup reel are comprised of a material selected from a group consisting of high strength plastic, polyimide, carbon com-posite, aluminum, beryllium, and combinations thereof.

23. The system of claim 21 wherein speed of said feed reel and said takeup reel is variable.

25 24. The system of claim 21 wherein speed of said feed reel and said takeup reel is synchronized to pulsing of said laser beam.

25. The system of claim 21 wherein said speed of said feed reel and said takeup reel is proportionate to burn rate of said

30 propellant targets. 26. The system of claim 21 which further includes a con-

troller. 27. The system of claim 21 wherein said ignition chamber

further includes a plurality of containment walls.

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